Fuse attachment



April 9, 1957 A, LANG 2,788,423

FUSE ATTACHMENT Filed May 6. 1955 trons (rent or trans ucent ADOLPH LANG INVENTOR.

AGENT United States Patent 2,788,423 FUSE ATTACHMENT Adolph Lang, New York, N. Y. Application May 6, 1955, Serial No. 506,530 2 Claims. (Cl. 200-121) The present invention relates to an attachment for electric safety fuses adapted to facilitate the ascertainment of the condition of a fuse, i. e. whether the same is intact or burnt out (blown).

in my earlier U. S. Patent No. 2,659,789, issued 17 November 1953, I have disclosed an attachment of this general character, comprising a light-transmission disk with a phosphorescent coating which lights up in response to a flash occurring within the fuse and retains its luminosity for a considerable time after such flash; this attachment further includes an opaque supporting ring for the luminous disk designed to shield it from light rays emitted by adjacent fuses or other extranaeous light sources, thereby preventing false excitation of the phosphorescent material.

Although the device described and claimed in my aforementioned patent is adapted to indicate at a glance, and even from a certain distance, the condition of a particular fuse where one or more such fuses are located in a dark room, as in the cellar of a building, or are normally enclosed within an opaque box, it is often unavoidable for a person inspecting or exchanging the fuses to admit some outside light to the fuse panel, whereby the indicator attachments of all the fuses will be lit and the detection of a blown fuse will be made diflicult for an extended period.

It is a principal object of my present invention to provide a phosphorescent indicator element for an electric fuse in combination with means for differentiating between a state of luminosity of the phosphorescent element due to illumination from without and a state of luminosity arising from the occurrence of a flash within the fuse to which the indicator element is aifixed.

A more particular object of my invention is to provide an attachment of the type set forth in which only a distinctive portion of the phosphorescent element is excitable by a flash within the fuse whereas substantially the entire visible surface of this element is lit in response to illumination from without.

A further object of my invention is to provide means in a fuse for imparting some luminosity to it even in its intact condition, thereby facilitating location of the fuse, but for giving a different and distinctive luminous appearance when the fuse is blown.

A feature of my present invention resides in the provision of a partly light-transmissive (transparent or translucent), partly opaque mask so inserted between the interior of the fuse and the preferably disk-shaped phosphorescent element that part of this element will be shielded from light rays emanating from the incandescent fusible strip of the fuse. This mask may be so shaped that either its opaque or its light-transmissive portions spell out a characteristic symbol, such as the letters NG, to convey the message that the fuse is not good when the symbol appears.

Reference is now made to the accompanying drawing showing a preferred embodiment of my present invention. In the drawing:

Fig. 1 is a view similar to Fig. 1 of my aforementioned patent, showing in longitudinal section a conventional electric fuse with an attachment according to the invention affixed thereto;

Fig. 2 is a rear end view, similar to Fig. 3 of my said patent, of the fuse and attachment shown in Fig. 1;

Figs. 3, 4 and 5 are perspective views of the mask, the phosphorescent element and a cover disk, respectively, forming part of the attachment shown in Figs. 1 and 2; and

Fig. 6 is a side view of the same attachment.

The electric safety fuse 10, for a more detailed illustration of which the reader is referred to my aforementioned patent, comprises a body 11 of insulating material, a glass housing 12 receiving part of said body, a metal shell 13 threadedly engaging the housing 12 and bearing against a shoulder 14 of the body 11 to keep same in engagement with the housing 12, and a fusible strip 15 conductively connected between the shell 13 and a central terminal 16.

The attachment 20 comprises a retaining ring 21 having resilient prongs 22 adapted to engage the front flange 17 of housing 12, thereby removably securing the attachment to the fuse 10. Ring 21, whose forward edge is bent over at 23, is internally provided with an annular shoulder 24. Clamped between shoulder 24 and edge 23 are an outer transparent disk 25, a disk 26 of phosphorescent material and an inner transparent (or at least translucent) disk 27.

Outer disk 25, which may be of glass, forms a protective lid for the assembly 26, 27 and may carry a suitable legend 2521, e. g. the words NG Shows When Fuse Blows, as shown in Fig. 5. Disk 27 has a lightransmissive portion 27a and an opaque portion 27b spelling out the letters NG as shown in Fig. 3. Phosphorescent disk 26 may be physically independent from disks 25, 27, as shown in Fig. 4, or may form a coating on one of them, e. g. as shown for the elements 25, 27 in my aforementioned Patent No. 2,659,789. It is to be understood that disk 26 will in either case be thin enough so as to appear illuminated from without when exposed to light from within fuse 10.

Disk 26 is provided with a central aperture 28 to enable visual inspection of the fusible strip 15 without removal of the attachment 20 from the fuse 10. Disk 27 is shown provided with a similar central aperture 29 which is of importance only, for the purpose just mentioned where this disk is merely translucent.

From the foregoing description it will already be apparent that the incandescence of strip 15, upon a blowing of fuse 10, will excite to luminosity only those parts of phosphorescent disk 26 which register with the lighttransmissive portion 27a of mask 27, whereby the letters NG will be distinctively visible when the disk 26 is viewed through cover 25. If, on the other hand, light falls upon disk 26 from the outside, i. e. by way of disk 25, the entire visible surface of disk 26 will be illuminated, whereby only the legend 25a will appear dark against a light background. I have found that, once the fuse has blown, the letters NG will remain clearly noticeable even if considerable light is thrown upon the outer surface of disk 26.

The opaque portion 27b of disk 27 perferably consists of a coating of paint or the like of low heat conductively, in order to minimize the thermal excitation of the shielded portions of element 26 the flash of the fuse.

My invention is, of course, not limited to the specific embodiment particularly described and illustrated. Thus, it will be readily understood that the light-transmissive portion 27a of mask 27 may be suppressed entirely, whereby only the opaque letters NG (or their con1- plement) will be in contact with the inner face of 3 phosphorescent element 2 6. Also, the character of the legends 25a, 27b may be varied at will and the legend 25a may be omitted if desired. Again, the phosphorescent element 26 with its mask 27 may be permanently secured to the fuse it on either side of the window portion 18 thereof, instead of being removably attached thereto'by means of a detachable support 21, 22. Various modifications and adaptations are, accordingly, possible without departing from the spirit and scope of the invention as defined in the objects and in the appended claims.

I claim:

1. In an electric fuse, in combination, a fusible member, a phosphorescent element positioned to receive light rays from said member upon incandescence of the latter, and masking means interposed between said member and said element in a manner shielding part of said element from said light rays, said masking means forming a distinctive pattern in registry with a surface portion of said element positioned to be'visiole from Without.

2. The combination according to claim 1, wherein said masking means is a partly light-transmissive, partly opaqueplate overlying at least a major portion of said element.

References Cited in the file of this patent UNITED STATES PATENTS 1,666,339 Miller Apr. 17, 1925 2,115,469 Quisling Apr. 26, 1938 2,659,789 Lang Nov. 17, 1953 

